Method of improving the properties of a ferrous metal in the molten state



6, 1969 HY. KARINTHI ET AL 3,484,232

METHOD OF IMPROVING THE PROPERTIES OF A FERROUS METAL IN THE MOLTENSTATE Filed Sept. 26. 1966 United States Patent METHOD OF IMPROVING THEPROPERTIES OF A FERRUUS METAL IN THE MOLTEN STATE Pierre Yves Karinthi,Champigny-sur-Marne, France, and Etienne Spire, Montreal, Quebec,Canada, assignors t0 LAir Liquide, Societe Anonyme pour IEtude etlExploitation des Procedes Georges Claude, Paris, France Filed Sept. 26,1966, Ser. No. 581,920 Claims priority, application France, Oct. 21,1965, 35,745; Aug. 10, 1966, 72,625 Int. Cl. C21c 7/00 US. CI. 75-45 12Claims ABSTRACT OF THE DISCLOSURE A halogenated compound is brought inliquid phase into contact with a porous device which on its oppositeside contacts molten ferrous metal. The halogenated liquid is forced bygas pressure through the porous device and into the molten metal. Thehalogen may be used to remove unwanted elements from the metal. Thenonhalogen part of the compound may combine with elements dissolved inthe metal or may itself dissolve in the metal.

This invention relates to a method of improving the properties of asteel or a cast iron by treating it in the molten condition.

The invention is characterised by the fact that there is injected intothe molten metal, in the liquid or vapour state, mixed or not mixed withinert gas, through a permeable wall, a halogenated compound which isforced through said wall by gas pressure and which, having possiblydecomposed on contact with the molten metal or in contact with asumciently hot portion of permeable wall, reacts chemically with themolten metal and improves the properties of the metal obtained, eitherby modifying its quality, or by modifying its composition.

This injection enables use to be made of halogens, or

elements combined therewith, or both in a form easy to handle and oftenless onerous than when these reagents are' used as in the prior art. Inaddition, the method of injection, which is easy to carry out, impartsgreat efficiency to the reagents because they are thereby finelydistributed in the liquid metal.

The following uses of the method of the invention, which are merlynon-limitative examples can be quoted:

(A) Selective elimination and possibly recovery of the manganese in castiron intended in particular for the manufacture of cast iron comprisingspheroidal graphite in a ferritic matrix, for example, by means ofcarbon tetrachloride, trichlorethylene, perchlorethylene,polyhalogenated derivatives of the hydrocarbons marketed under the nameFreons, and lead dichloride. These reagents react through their halogenswhich combine with the manganese to give a volatile compound.

By way of example, a 100 kg. charge of a cast iron containing:

Percent C 3.8 Si 0.8 Mn 0.85 P 0.1

was treated by blowing in liquid CCl After blowing in 2.2 kg. of CCl,for six minutes, the manganese content was brought to 0.06%, the siliconcontent remaining unchanged. Thus, 93% of the initial manganese waseliminated.

(B) Fixing the carbon, for example by means of titanium trichloride,titanium tetrachloride, zirconium tetrachloride and niobiumpentachloride, particularly in stain- 3,484,232 Patented Dec. 16, 1969less steels, extra-mild steels for sheet intended for enamelling, and inall ferrous metals in which this fixation is beneficial. These reagentsreact through their metal. It is known that certain ferro-titaniums,notably the conventional composition containing 30% of titanium, aredifiicult to dissolve in ferrous metals.

(C) Incorporation of small quantities of an element to give increasedefiiciency, for example the addition ofboron to steels by theintroduction of boron trichloride.

(D) Refining the grain of steel, for example by the introductionaccompanied by increased yield, of niobium pentachloride in carbonsteels for sheets having a high elastic limit and intended, for example,for use in the manufacture of pipes for carrying fluids under pressure;the niobium resulting from the decomposition of its chloride refines thegrain of the steel.

The above-mentioned elimination of manganese is achieved by halogenationusing inexpensive reagents and the method of introduction used gives ahigh yield on the part of the reagent because it is thereby finelydistributed in the liquid metal. Furthermore, the recovery, from thefumes given off, of the manganese chloride, provides a valuableby-product. This elimination generally calls for 1.3 to 5 kg. ofchlorine per kg. of manganese to be removed: carbon tetrachloride, ifthis is used for the injection, contains 92% of chlorine. The recoveryof the manganese can be carried out by bringing the vapour into contactwith water which dissolves the manganese chloride and iron chloride, theiron chloride being precipitated, then by subjecting the remainingsolution to electrolysis, to obtain the manganese.

The incorporation of small quantities of an alloying ele ment, using acompound which decomposes, has already been proposed. The compound inquestion was a metal carbonyl which is a costly reagent; furthermore, itwould have been poorly utilised because it was proposed to introduce itthrough a single orifice which would have produced large bubbles. Thepresent invention, on the other hand, permits the use of a relativelyinexpensive reagent, and permits it to be employed very efiiciently, incontrast to the conventional ferro-alloys, the yields from which are inthe order of 60% Generally, the weight of reagent introduced does notexceed 1% of the weight of the metal treated.

The invention will again be described hereunder by reference to theattached drawing in which:

FIGURE 1 represents the general arrangement of the treatment vessel andof the auxiliary vessel for introducing the reagent;

FIGURE 2 shows a different embodiment of the same general arrangement;

FIGURE 3 represents a variant in which the auxiliary vessel is in theform of a plunger tube having a perme. able base;

FIGURE 4 shows a variant of the equipment of FIG- URE 2, in which thereagent is vaporized before being introduced.

In FIGURE 1 there is shown a vessel 1, the base of which is providedwith a permeable plug 2. The rear portion of this plug is surrounded bya fluid-tight envelope 3 connected by a pipe 4 to an auxiliary vessel 5containing the halogenated compound to be forced into the plug. The pipe4 passes into this vessel through a plunger tube 6. A pipe 7 connectsthe vessel 5 to a gas cylinder 8, provided with a control valve 9 and amanometer-flowmeter unit 10. The vessel 5 is further provided with adischarge pipe 11 fitted with a valve 12. Finally, the vessel 5 can beplaced on a balance 13 so as to facilitate the measuring out of theliquid forced via the pipe 4 and control valve 14 through the porousplug.

FIGURE 2 represents a variant in which the auxiliary vessel 34 isattached to the treatment vessel 1 and is fixed in alfluid-tight mannerbeneath the base of this latter vesse A forcer pipe is arranged in theform of a plunger tube 37 directed towards the base of the auxiliaryvessel. As previously, this latter vessel is provided with apressurizing pipe 7 connected to a gas cylinder 8, and with a dis chargepipe 11. Finally, it is optionally provided with heating meansrepresented symbolically by an electric coil 15. This could be aresistance or an inductance coil, or could even be replaced by a spiralsteam pipe.

The halogenated compound can thus be loaded into the auxiliary vessel inthe solid condition, then melts when it is to be forced up through theporous plug 2.

If need be, the halogenated compound could initially be contained, inthe solid, liquid, or even gaseous state, in an ampoule or a sealedcartridge fitted with a fusible plug or with a plug which could bebroken by a magnetic hammer or any other equivalent means.

Optionally, treatment vessel 1 is provided with a fluidtight cover 16connected by piping 17 to a vacuum pump (not shown).

The injection equipment shown in FIGURE 3 is in the form of a refractoryplunger tube 18 closed by a porous plug 19. The tube 18 has in its axisa cavity 20 surrounded by a coil 21 intended to melt the halogenatedcompound 22 previously introduced in the solid condition into the cavity20. This cavity is connected by a pipe 23 to a source of inert gas, notillustrated.

The tube 18 is plunged into the bath of metal to be treated, in suchmanner that its porous mouthpiece 19 is located below the surface 24 ofthe bath.

FIGURE 4 shows a variation of equipment of FIG- URE 2 in which theauxiliary vessel 34 is provided, at its base, with a porous plug fittedwith a fluid-tight envelope 26 connected to a gas pipe 7. This vessel isoptionally provided with a heating coil 15. The bubbling of gas throughthe plug 25 and then through the halogenated reagent brought to theregion of its boiling point entrains a certain quantity of this reagentin the diluted vapour state. This diluted vapour, together with the gasenters the metal bath through the permeable element 2 which separatesthe treatment vessel 1 and the auxiliary vessel 34. In this manner, thereagent passes into the metal to be treated, forcing through afluid-permeable wall pressure at the temperature obtaining in theauxiliary vessel.

What we claim is:

1. A method for improving the properties of a ferrous metal, comprisingestablishing a bath of molten ferrous metal to be treated, forcingthrough a fluid-permeable wall and into the bath a halogen-containingfluid that is chemically reactive with at least one component of thebath, the halogen of said fluid being present in the form of ahalogenated compound selected from the class consisting of halogenatedhydrocarbons and lead dichloride, said bath containing manganese to beat least partially eliminated by said halogenated compound, andrecovering manganese from fumes evolved from the bath.

2. A method for improving the properties of a ferrous metal, comprisingestablishing a bath of molten ferrous metal to be treated, and forcingthrough a fluid-permeable wall and into the bath a halogen-containingfluid that is chemically reactive with at least one component of thebath, said halogen of said fluid being present in the form of ahalogenated compound selected from the class consisting of titaniumtrichloride, titanium tetrachloride, zirconium trichloride, and niobiumpentachloride, said bath containing carbon to be fixed by saidhalogenated compound.

3. In a method for improving the properties of a ferrous metal,comprising establishing a bath of molten ferrous metal to be treated,and forcing through a fluidpermeable wall and into the bath ahalogen-containing fluid that is chemically reactive with at least onecon? ponent of the bath; the improvement comprising bringing saidhalogen-containing fluid into contact with said fluidpermeable wall as aliquid under pressure.

4. A method as claimed in claim 3, and applying pressure to said liquidby means of a gas under pressure.

'5. A method as claimed in claim 3, the halogen of said fluid beingpresent in the form of a halogenated compound the nonhalogen part ofwhich remains in the bath.

6. A method as claimed in claim 5, said nonhalogen part being boron.

7. A method as claimed in claim 3, the ferrous metal being carbon steeland the halogen of said fluid being present in the form of a halogenatedcompound the nonhalogen part of which refines the grain of the steel.

8. A method as claimed in claim 3, the halogen of said fluid beingpresent in the form of a halogen compound whose decompositiontemperature is lower than the temperature of the bath.

9. A method as claimed in claim 3, the halogen of said fluid beingpresent in the form of a compound whose decomposition temperature islower than the temperature of at least a portion of said wall.

10. A method as claimed in claim 3, the halogen of said fluid beingpresent in the form of a halogenated compound selected from the classconsisting of halo genated hydrocarbons and lead dichloride, said bathcontaining manganese to be at least partially eliminated by saidhalogenated compound.

11. A method as claimed in claim 10, and recovering manganese from fumesevolved from the bath.

12. A method as claimed in claim 3, in which the halogen of said fluidis present in the form of a halogenated compound selected from the classconsisting of titanium trichloride, titanium tetrachloride, zirconiumtrichloride, and niobium pentachloride, said bath containing carbon tobe fixed by said halogenated compound.

References Cited UNITED STATES PATENTS 2,134,905 11/1938 Bamfylde -59 X2,871,008 1/ 1959 Spire 266-39 FOREIGN PATENTS 590,537 1/ 1960 Canada.619,017 4/ 1961 Canada. 739,408 7/ 1966 Canada. 1,146,218 5/1957 France.

977,105 12/ 1964 Great Britain. 999,482 7/ 1965 Great Britain.

RICHARD O. DEAN, Primary Examiner U.S. Cl. X.R.

